基于离散元法的百合鳞茎弹性多趾揉搓辊组设计与试验

Design and Experiment of Elastic Multi-toed Rubbing Roller Group for Lily Bulbs Based on Discrete Element Method

摘要:

针对百合鳞茎机械化收获程度低且茎-土分离效果差、损伤严重等问题，本文基于百合鳞茎基本物理力学特性，运用仿生学原理，设计了一种弹性多趾揉搓辊组。通过测量百合鳞茎基本物理力学参数，得到其平均尺寸为83.7mm×74.6mm×49.0mm，密度为1.09g/cm3，与聚氨酯材料静、动摩擦因数分别为0.50、0.42。根据百合鳞茎采收要求，建立百合鳞茎在弹性多趾揉搓辊组上的动力学微分方程，得到影响其收获性能的关键因素包括：揉搓趾长L、辊轴转速ω和单周趾数N。在EDEM软件中建立弹性多趾揉搓辊组-土壤-百合鳞茎互作用仿真模型，以百合鳞茎明茎率Y1、最大碰撞力Y2为评价指标，运用Box-Behnken中心组合设计方法开展三因素三水平正交试验，通过构建目标函数以及约束条件进行优化逼近，确定最优参数组合：L为52mm、ω为54r/min、N为6，在最优参数组合下，Y1为97.25%、Y2为12N。田间试验结果表明，明茎率与最大碰撞力仿真值与试验值相对误差分别为1.51%和21.05%，且试制的弹性多趾揉搓式百合收获装置较传统输送链式收获装置明茎率提高3.3%、损伤率降低13%，具有优异的收获性能，能够满足根茎类中药材收获机质量评价相关要求。研究结果可为根茎类中药材机械化收获提供方案。

Abstract:

Aiming at the problems of low mechanization degree and poor stem-soil separation effect as well as severe damage during the mechanized harvesting of lily bulbs, based on the basic physical and mechanical properties of lily bulbs, a set of elastic multi-toed rubbing roller group was designed by applying bionics principles. By measuring the basic physical and mechanical parameters of lily bulbs, it was found that their average size was 83.7mm×74.6mm×49.0mm, density was 1.09g/cm3, and the rolling friction coefficient with polyurethane material was 0.42, while the static friction coefficient was 0.50. According to the requirements of lily bulb harvesting, the dynamic differential equation of lily bulbs on the elastic multi-toed rubbing roller group was established. The key factors affecting the harvesting performance of lily bulbs were found to be: the length of the rubbing toe (L), the rotational speed of the roller shaft (ω), and the number of toes per week (N). A simulation model of the interaction between the elastic multi-toed rubbing roller group, soil, and lily bulbs was established in the EDEM software. With the clear stem rate Y1 and the maximum collision force Y2 of lily bulbs as evaluation indicators, a three-factor three-level orthogonal experiment was conducted by using the Box-Behnken central composite design method. Through the construction of the objective function and constraint conditions for optimization approximation, the optimal parameter combination was determined as: L was 52mm, ω was 54r/min and N was 6. Under the optimal parameter combination, the clear stem rate Y1 of lily bulbs was 97.25% and the maximum collision force Y2 was 12N. Field experiments verified that the relative errors between the simulation values and the experimental values of the clear stem rate and the maximum collision force were 1.51% and 21.05%, respectively. Moreover, the trial-made elastic multi-toed rubbing lily harvesting device, compared with the traditional conveyor chain-type harvesting device, increased the clear stem rate by 3.3% and reduced the damage rate by 13%, demonstrating excellent harvesting performance, and meeting the relevant requirements for the quality evaluation of root and rhizome Chinese medicinal material harvesters. The research results can provide a solution for the mechanized harvesting of root and rhizome Chinese medicinal materials.